Sciency Words: The Darian Calendar

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


In 1986, aerospace engineer and polymath Thomas Gangale published a paper titled “Martian Standard Time” in which he outlined a calendar which could be used by Martian colonists in the future. Gangale named this calendar the Darian calendar after his son, Darius, and he describes the idea in greater detail on his website (click here).

According to the Darian calendar, the Martian year begins on or around the vernal equinox, when the sun is directly above the planet’s equator and spring is just beginning in the northern hemisphere. Because the Martian year is nearly twice as long as Earth’s, we get twenty-four months rather than twelve.

The names of the months alternate between the Latin and Sanskrit names for the Zodiak constellations. Thus the month of Sagittarius (the first month of the year) is followed by Dhanus, then Capricornus, then Makara, then Aquarius, and so on until you get to Scorpius and then Vrishika (the last month of the year). Each month has 28 days… sorry, 28 sols… except Kumbha, Rishabha, Simba, and Vrishika (the 6th, 12th, 18th, and 24th months, respectively) unless it’s a leap year, in which case Vrishika is 28 sols long.

And regarding leap years, there are a lot of them: six every decade, so leap years are actually more common than regular years. But then every hundred years we have to take a leap sol away, and then every five hundred years we have to put it back—I know, this is starting to sound complicated, but it’s not that much worse than what we have to do to keep the Gregorian calendar balanced on Earth.

If you’re wondering about the days of the week (I mean, sols of the week), Gangale thought of that too. Each Mars week is made up of seven sols with names that hark back to the ancient Latin names for the days of the week:

Sol Solis (Sunday)
Sol Lunae (Monday)
Sol Martius (Tuesday)
Sol Mercurii (Wednesday)
Sol Jovis (Thursday)
Sol Veneris (Friday)
Sol Saturni (Saturday)

Also, Gangale designed his calendar so that each date always falls on the same sol of the week. The 1st of Sagittarius is always a Sol Solis, for example. That’s pretty convenient, I think, although it also works out that every month the 13th is always on a Sol Veneris (a Friday), which seems rather unlucky.

The question, of course, is will Martian colonists actually adopt this as their calendar? I don’t know, but it seems certain aspects of the Darian system—such as the way it handles leap years—have already been borrowed for other Mars-related research purposes.

8 thoughts on “Sciency Words: The Darian Calendar

  1. I can’t imagine Martians wanting to deviate from the usual Monday, Tuesday, … days of the week, and I wonder if they would really adopt a new system for months? Interesting question – what would deep space travellers adopt as their date system?

    Liked by 1 person

    1. I guess the issue with Monday is that the word “day” is in it, but I doubt that would really bother Mars colonists that much. The thing about making up new names for the months felt a little unnecessary to me as well.

      As for travel in deep space, I’d guess you could set your clocks to run however you want them to run: Earth time, Mars time, or whatever. I don’t know, but it’s definitely an interesting thing to think about.


      1. I remember when I was in school the teachers saying we were going to switch to Metric and that’s why we we’re learning it.

        I’m not sure how people who’s birthday NEVER falls on a weekend would feel though 🙂

        Liked by 1 person

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